Living polymerization, which is a type of precision polymerization, helps control molecular weight, molecular weight distribution, and the like, and is accordingly applied to processes for preparing various types of functional materials, such as terminal-functional polymers, block polymers, and graft polymers. In particular, one of the living polymerization, atom transfer radical polymerization, serves many uses because it can be performed under moderate conditions with use of a wide range of vinyl monomers. One example of atom transfer radical polymerization is a polymerization system in which an organic halide or a halogenated sulfonyl compound is used as an initiator and a metal complex containing a Group 8, 9, 10, or 11 element of the periodic table as the central atom is used as a catalyst (see, for example, Matyjaszewski et al., J. Am. Chem. Soc. 1995, 117, 5614, Macromolecules 1995, 28, 7901, Science 1996, 272, 866; Sawamoto et al., Macromolecules 1995, 28, 1721). Vinyl polymers prepared by these polymerization processes have a halogen at the terminus of the polymers.
Although vinyl polymers containing a halogen are used as intermediates for various processes for preparing functional materials, the halogen remaining the polymer can cause a problem. For example, (1) a free acid derived from the halogen may negatively affect product quality and production equipment; or (2) a radical generated by thermal dissociation of the carbon-halogen bond may cause the molecular weight and molecular weight distribution to increase. In vinyl polymers prepared by atom transfer radical polymerization, it is therefore necessary to remove the halogen from the vinyl polymer in some way.
On the other hand, vinyl polymers having a plurality of reactive functional groups in their molecule are cured by crosslinking with use of an appropriate cross-linker. In particular, vinyl polymers selectively having a reactive functional group at their termini result in cured materials having a high molecular eight between crosslinking points and superior rubber elasticity, and are accordingly used as various types of material. A reactive functional group can be introduced to a terminus of a vinyl polymer having a halogen at the terminus prepared by atom transfer radical polymerization, by use of the reactivity of the terminal halogen (Japanese Unexamined Patent Application Publication Nos. 11-080250, 11-005815, 09-272715, 2000-38404, 2000-44626, and 2000-128924).
Methods of introducing a functional group by replacing the halogen with use of an agent having a reactive functional group (Japanese Unexamined Patent Application Publication Nos. 11-080250, 11-005815, 09-272715, 2000-38404, and 2000-128924) can simultaneously carry out the introduction of the functional group and the removal of the halogen. However, these methods limit the type of agent for the removal and require an additional step for removing the agent.
Another method of allowing an organic compound having an ethylenically unsaturated group together with a reactive functional group to react with the terminal halogenated (Japanese Unexamined Patent Application Publication No. 2000-44626) can easily introduce a functional group advantageously, but the halogen remains in the resulting polymer. The inventers of the present invention developed a process for removing the halogen by use of an oxyanion compound (Japanese Unexamined Patent Application Publication No. 2000-344831). This invention helps remove the halogen at a terminus of a vinyl polymer. It has however been found that a vinyl polymer with a silyl group produced by the process of the present invention does not have long-term stability in storage, and that it requires to be purified using a large amount of adsorbent after removal of the halogen in order to improve the long-term stability.
For removing the halogen of a vinyl polymer produced by atom transfer radical polymerization, a process performing an addition/elimination reaction in the polymer with use of a specific removing agent has been disclosed (WO99/54365). Unfortunately, this process limits the type of removing agent, and accordingly it is not easy to introduce a functional group. In addition, elimination produces a free acid.